Science M.C.Q

Potassium (K) forms a basic oxide and has an atomic number of 19. The atomic numbers of 18, 17 and 14 correspond to acidic oxides.

L is the valence shell for elements of the second period of the modern periodic table, since the period number is decided by the number of valence shells.

R (Si) is a metalloid since its atomic number is 14 and it has 4 valence electrons.

The modern periodic table of elements was prepared by Neils Bohr.

The increasing order of the atomic radii of oxygen, fluorine and nitrogen is fluorine, oxygen and nitrogen. This is because the atomic radius decreases from left to right in a period.

The three elements having the chemical symbols Si, B and Ge are metalloids.

In the modern periodic table, there are 18 vertical columns known as groups.

The element with an electronic configuration of (2, 8) belongs to group 18 (noble or inert gases) of the periodic table, as the elements in this group have their valence shell completely filled with electrons.
Group number = valence shell + 10
= 8 + 10 = 18.

The Newlands' law of octaves for the classification of elements was applicable only up to the element calcium.

Potassium (K) with an atomic number of 19 has the largest atomic radius. This is because sodium and potassium are elements of group 1. On moving from top to bottom in a group, the atomic radius increases. Magnesium and calcium are elements of group 2. The size of the atomic radius decreases on moving from left to right in a period of the periodic table.

The element which can form an acidic oxide should be the one with atomic number 16. Sulphur has an atomic number of 16 and sulphur oxide is acidic.

C and D.

The isotopes of chlorine, having different atomic masses but same atomic numbers are kept in the same group in the modern periodic table.

Isotopes of an element have the same atomic number and the same chemical properties.

Be, Mg and Ca are elements of group 2, written in order of their increasing metallic character. On moving down in the group, the metallic character increases.

F is the element that does not lose an electron easily, as it is a non - metal (halogen) belonging to group 17 of the periodic table.

Germanium (eka - silicon) is the element which found a vacant place in the periodic table later on.

K would lose an electron easily as it is a group 1 metal whose atomic number is greater than that of Na, which also belongs to group 1. Mg and Ca are group 2 metals and the tendency to lose electrons decreases on moving from left to right in a period of periodic table.

The number of valence electrons does not increase while moving down the group in the periodic table.

The size of the atom decreases on moving from left to right in a period of the periodic table. With an increment in the atomic number, both the proton number and the nuclear positive charge increase. As the nucleus attracts the outermost electron, the size of the atom decreases.

On moving from left to right in the periodic table, the tendency of an atom to lose electrons decreases.

Proton is an atomic particle whose number in the atoms of an element remains the same always, and forms the real basis for the modern classification of elements.

In Mendeleev's periodic table, a gap was left for gallium, scandium and germanium.

According to Mendeleev's periodic law, the elements in the periodic table were arranged in the order of increasing atomic masses.

B, C and D, with atomic numbers 3, 7 and 10 respectively, belong to the same period of the periodic table. This is because the elements B, C and D have the same valence shell (L shell).